Extensometer



June 21, 1960 Filed Aug. 21, 1958 F. C. HUYSER EXTENSOMETER 2Sheets-Sheet l I6 I7 5059 55 Q5 Y. A in t? y a I 6| a?,

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Af/ des is 5 +S se H+ INVENTOR BY FRANClS C, HUYSER MMA, W, wf/emATTORNEYS June 21, 1960 F.c. HUYsER 2,941,298

EXTENSOMETER Filed Aug. 2l, 1958 2 Sheets-Sheet 2 INVENToR FRANCIS c.HuYsER BY Maz/Z1, Wj wmv ATTORNEYS tlinues beyond the Ayieldpoint,`highUnited States Patent O nXTnNsoMnrnR Francis C. Huyser, Moline, lll.,assiguor to American Machine and Metals, Inc., New York, N.Y., acorporation of Delaware Filed Aug. 21, 195s, ser. No. 756,334 1o claims.(ci. :i3-14s) v sufficient magnification, sensitivity, and accuracy.Thus,

inV a test involving extensive elongation of the specimen,

the conventional extensometer gives a magnified measuref K ment of thedeformations in the early part of the test only, while post-test directmeasurements of the specimen are needed to determine the completeelongation. In the case of a tension test of a steel specimen torupture,

nication is initially needed to indicate the small deformationsoccurring in-the elastic range. When the test con# elongation capacitykin place of high magnification is requiredL of the extensometer. in theregion beyond the yield point,l the slope of the stress-strain Vcurve isquite low compared tothat of the elastic region and portions immediatelybeyond it. These characteristics of steel specimens, as an example,

go to show the particular measurement problems that the extensometermust overcome.A

One of the objects of the present invention to provide an extensometerfor use in accurately measuring and recording the elongations of aspecimen stressed in aV materials testing machine over a large range ofelongation. Another of the objects of this invention is to pro vide anextensometer for the above purpose which measures and records theelongation of a specimen initially at one degree of magnification andsubsequently at a different degree of magnification.

" tively cover a broad range of elongation. This can be accomplished byan extensometer including a supporting frame with a fixed gauge pointattached to the frame.

A moveable gauge point is mounted on a lever which is pivotally attachedto the frame, both of the gauge points contacting a test specimen. Asecond lever is pivotally attached to the supporting frame rotating inthe `same general plane as the first lever, alongwhich are placed twobearing means or two projections, one or the other of= which contactsthe second lever, so that as the first -lever rotates due to elongationof the specimen, the

resultant lever arm of the two levers will change in length fuponcontact to the second lever, changing from one to the other of thebea-ring means or projections. A moveable pick-up or signal means may besuitably mounted I on thehsupporting frame and connected to the second asensitive extensometer and one capable of high mag -lever so as to bedisplaced in response to movement of the moveable gauge point andthereby provide a signal for measuring the deformation of a stressedspecimen.

Other objects, advantages and features of the invention will becomeapparent from the following description and drawings which are merelyexemplary.

In the drawings:

Fig. l is a top plan view of an extensometer embodying the presentinvention.

. Fig. 2 is `a vertical sectional 'view of the extensometer as viewed indirection of the arrows 2 2 on Fig. 1. Fig. 3 is a fragmentary verticalsectional view of the extensometer showing the extensometer afterlimited elongation of the specimen.

Fig. 4 is a fragmentary vertical sectional view of the extensometershowing the extensometer after large elongation of the specimen. A

Fig. 5 is an end elevational sectional view of -the extensometer asviewed in the direction of the arrows 5 5 on Fig. 2.

Fig. 6 is an end elevational sectionalsview of the e'xtensometer asviewed in the direction of the arrows 6-6 of Fig. l.

Fig. 7 is a fragmentary end elevational view of the extensometer asviewed in the direction of the arrows 7--7 in Fig. 2.`

The extensometer is generally shown in Figs. `1 and 2. To frame 8, thereis attached'bracket 9 by 'means of screw 10. Fixed knife edge 11 whichis` attached'to bracket 9 by'screws 12, contacts theY upper portionofthe specimen 13, which is'stressed in a conventional test- 'tached byscrew 17. Spring-'18forces' lever 14 so-that moveable knife edge- 16 isurged in the directionaof fixed knife edge 11. `As shown in-Fig. 7, stop19 is mountedjon bracket 9 andfserves to-limit the upward travel ofknife edge `16 caused by the upward motion of lever 14. Stop,19 issecured to bracket 9 by means of screw 20 which is in turn locked by setscrew 21. The lower edge 22 of stop 19 contacts the upper `surface 23 ofmoveable knife edge 16, when the knife edge is inits uppermost position.Upon assembly of the instrument, the lower Vedge 22 is adjusted so thatcontact of moveable knife edge 16 with stop 19 locates the moveableknife edge initially at the required gauge length from the fixed knifeedge 11. As shown in Figs. l and 5, plate 24 containing slot 25 isattached to frame 8 by means of attaching screw 26. Slide 27 is fittedinto slot 25 and to it is attached `block 28 by means of screw 29. Plate24 (Figs. land 6) contains a slot 3b beginning at point 31 vandextending toward its free end. Lug 32 attached to block 28 by means ofplate 33 and screw 34 serve to guide block 28 with respect to slot 30 inplate 24. To thefree vend of plate 24 is attached plate 35 by means ofscrews I36. Plate 35 contains a tapped hole 37 so as to receiveadjusting screw38, whose linear motion is transmitted to spring 39through collar 40 which is free to turn upon screw 38. Movement ofadjusting screw permits block 28l to be positioned toward specimen' 13.Resilient bracket 41 mounted onblock 28 by means of .screw 42 transmitsmotionr of block 28 to, clamp 43 soas to hold the knife edges rmlyagainst the test specimen. Screw 44 and lock nut 45 serve to attach theresilient bracket 41 Ito clamp 43. Spring 39 permits, clamp 43 to bepreloaded against specimen 13 by adjustmentr of 49. toward lever 14.

. upper surface.

.sion by the testingA machine.

ldue; to the action of, clamp compensated for by suitable that4 theinitial small deformations of specimen specimen 13 has been ananas/s,

L, An additional lever 49 (Fig. 2.) is pivotally attached Ato, frame 8Vby means of at spring 50 which is secured to, lever 49 by screw 51. Thexed' end of spring S0 is mounted on frame 8 by means of support 52.Support 52 is heldv to fratrie 8 by mounting screw 53V while set screw54 permits theV angle. between support 52 and frame 8 to be properlyadjusted. Flat spring 56 forces lever Balls 55 and 56 are mounted onlever 14 by means vof sockets 57 and 58. Under the urging of` spring5,0, surface 59 of lever 49 is in contact with ball 55. Lever 49 isprovided with ball 60 on its Pick-up device 61 is mounted on support.`8. This device may, be a differential transformer whose core 62 restson ball. 60 by means of extension 63 and follower k64. The winding ofthe. trans- .former 65 surrounds core -62 in the conventional manner.

In operation, the specimen 13 may be stressed in ten- Knife edges 11 and16 are held in firm contact with specimen 13 by the force 43. Uponelongation of specimen 13, lever. 1.4 as viewed in Fig. 2, begins adownward motion from its initial position in which upper: surface 23 ofknife edge 16 was resting on surface 22' of stop 19; The downwardmovement of lever 14 is opposed by restraint of spring 18 at its pivotpoint.

Under the force of spring 5.0, leverY 49 isheld in con-` tact at itssurface 59: with b ll 55. Since core 62 of l-the differentialtransformer 61 is biased in a downward direction byl a spring not shown,follower 64 remains.

Ain contact with ball 60 as lever 49 moves in a downward direction.

vvF'fSince ball 55 is positioned along the lever 14 in from '-the'freeend of the lever, theball S5 experiences less linear motion vthan thatof knife edge 16v as the speci- -merr 13 is elongated. Thus,theelongation of specimen l13 is partially reduced as indicated at ball55.

Y In a ysimilar' manner, ball 60 of lever 49 is located in from ythepoint on surface 59 which rests on ball 55. "Thus, at'ball 60,- themotionof knife edge 16 has been "further reduced. Consequently, core -62of pick-up 61 merely travels a fraction ofthe distance travelled byknife edge 16. Thereduced motion of the core is fully electricalamplilication so clearly and accurately indicated.

Fig. 3 shows the specimen and extensometer after elongated to a markedextent. This could occur in testing a steel specimen when the 'stressapplied to :the specimen has been carried. appreciably beyond the yieldpoint. In further considering 'the example of a test involving a steelspecimen, it is well known that the slope of the stress-straincharacterlistie is of a much smaller value beyond the yield point. j Forthis reason, the magniiication` of the extensometer could be greatlyreduced and yet give usable indication. As shown in Fig. 3, knife edge1-6 has moved downward until spherical surface- 66 is nearly contacting,ball 56. When surface 66 contacts ball 56 and further y movement oflever 14 occurs, surface .59 of lever-49 ,i will lose contact, with ballS'. Adjustment of set screw 1 54 determines the position the pivot pointof at spring 50 for lever 49 which in turn determines the elongation ofspecimen 13 that is required to cause a transfer of lever 49 from.resting on ball. 55 to ball 56.

Fig. 4 shows the extensorneter after the specimen 13 has beenextensively elongated in a test wherein tensile rupture is approached.Due to the reducing action of levers 14 and 49, itis evident that knifeedge 16.; can experience very large displacement yet with va minimum ofdisplacement for extension63 of pick-up I61.

Lever 14 moves downward ball 55. lOSGSQQIl.-

13 are tact- With surface 59 of lever- 49. Sphericalv surface- 66 oflever 14 then rests uponball S6. It is apparent that a second form ofthe original compound lever system has been established. Since ball 56is greatly removed 5 from the free end of lever 14 and since the freeend of lever 49 in contact with ball 56 is at appreciable distance fromball 60, a muchV greater reduction of the indicated travel of knife edge16 V'has been effected. As shown` in the figures, the change in thereduction from vthe lfirst to. the. secoud'form, of the compou-ndleversystems is of a factor of approximately ten.

In the casewherelarge elongation has occurred, it is necessary for theframe 8 to rotate slightly clockwise as viewed in Fig. 4 so that knifeedge 16 may remain in contact with specimen 13. Resilient bracket 41exes suiciently to allow the frame to rotate and yet'keep clamp 43against the specimen 13.

It is to be. understood that details of the invention can be changed andmodifications may be effected therein 29 without departing from thescope or spirit of thev invencombination including, specimen dimensionresponsive change. means, a pair of lever means actuated by saidresponsive means, signal means actuated by one of said lever means, anda plurality of bearing means on one of said lever means adapted tocontact the other lever means, one of saidbearing means being contactedby the other lever means at av time so that the effective lever arm willbe changed. I

y `2. In a device for measuring the deformationl of a stressed specimen,the combination including supporting means, fixedgauge point meansattached to said supporting means, moveable gauge point means mounted onlever means pivotally attached to said supporting means, said fixed andYsaid moveable gauge point means contacting V saidspecinremr second levermeans pivotally attached -.to

said supporting, means and rotatable-in the same general l plane as saidfirst lever means, projection means on Yone of said levers, secondprojection means on one, of said lever means. in spaced yrelationshipalong the length of said lever means from said. irstrprojection, eachone of 45.Y said projection means onY one of said lever means alone4contacting the other of said lever means for a portion of. allpositionsof said first lever means, the total of said portions equaling allApositions of said first leverl means, so that upon angular movement ofsaid first lever means,

50. vthe resultant lever arrnfof. said first and said second lever meanswill change in length upon contact to the other lever means, changingfrom said rst to said second projectionV means, and moveable; pick-upmeans mounted on said supporting meansand connected to said second levermeans: tov be displaced relative to said supporting means in responsetodisplacement of said moveable gauge point means.

3. In a device for measuring the deformation of a stressed specimen, thecombination including support- 60. ingmeans, xed gauge point meansattached to, said sup- -portingmeans moveable gauge point means mountedon rst. lever means pivotally attached to said supporting means, ,saidiixed and said moveable gauge point means contacting said specimen,second lever means pivotally attachedv to;- saidi supporting meansV androtatable in .the

.same .plane as said iirst vlever means, a plurality of. pro- :jectinnVmeans spaced along the length of said lever means, each one of saidprojection means onA one of said lever'rneans alone contacting the.other of said lever means for a rangef of positions of said first levermeans sothatupon angular movement of said first lever means .theresultant lever arm o f said rst and said secondA lever means-inrementiallv in length for each projection means contacting a levermeans, and moveable pick-up means vmourned on said supporting means andAconnected to said second rever means to Vbe displaced relative to saidsupporting means in response to displacement of said moveable gaugepoint means.

4.V In a device for measuring thel deformation of a stressed specimen,the combination including supporting means, fixed gauge point meansattached to said supporting means, moveable gauge point means mounted onlever means pivotally attached to said supporting means, said fixed andsaid moveable gauge point means contacting said specimen, a plurality ofadditional lever means pivotally attached to said supportingmeans androtatable in the same plane as vsaid lever means, said plurality oflever means forming a compound lever means with said lever means, aplurality of projection means in spaced relationship along the length ofsaid lever means, each one of said plurality of projection means alonecontacting the adjacent lever means of said plurality of lever means fora portion of all positions of said lever means, the total of saidportions equaling all positions of said lever means, so that uponangular movement of said lever means, the resultant lever arm of saidlever means and said plurality of lever means will change in length uponcontact to said adjacent lever means changing from one to another ofsaid projection means, and moveable pick-up means mounted on saidsupporting means and connected to one of said plurality of lever meansto be displaced relative to said supporting means in response todisplacement of said moveable gauge point means.

5. In a device for measuring the deformation of a stressed specimen, thecombination including supporting means, fixed gauge point means attachedto said supporting means, moveable gauge point means mounted on levermeans'pivotally attached to said supporting means, clamping meansholding said gauge points in contact with said specimen, adjustableresilient bracket means attaching said clamping means to Said supportingmeans, a second lever means pivotally attached to said supporting meansand rotatable in the same plane as said first lever means, projectionmeans on one of said levers, second projection means on one of saidlever means in spaced realtionship along the length of said lever meansfrom said first projection, each one of said projection means on one ofsaid lever means alone contacting the other of said lever means for aportion of all positions of said first lever means, the total of saidportions equaling all positions of said first lever means, so that uponangular movement of said first lever means, the resultant lever arm ofsaid first and said second lever means will change in length uponcontact to the other lever means changing from said first to said secondprojection means, and moveable pick-up means mounted on said supportingmeans and connected to said second lever means to be displaced relativeto said supporting means in response to displacement of said moveablegauge point means.

6. ln a device for measuring the deformation of a stressed specimemthecombination including supporting means, fixed gauge point means attachedto said supporting means, moveable gauge point means mounted on firstlever means pivotally attached to said supporting means, said fixed andsaid moveable gauge point means contacting said specimen, second levermeans pivotally attached to said supporting means and rotatable in thesame plane as said first lever means, bearing means on one of said levermeans, said bearing means contacting said other lever means, so thatupon angular movement of said first lever means, the resultant lever armof said first and second lever means will vary in length for eachportion of said cam means contacting said second lever means, andmoveable pick-up means mounted on said supporting means and connected tosaid second lever means to be displaced relative to said supportingmeans in response to displacement of said moveable gauge point means.

7. In a device for measuring the deformation of a stressed specimen, thecombination including supporting means, fixed gauge point meanskattached to said vsup,- porting means, moveable gauge point meansmounted on lever means pivotally attached to said supporting means',said xed and saidmoveable gauge point means'fcon'- tacting saidspecimen, second lever means,l pivotal mounting means for said secondlever means adjustably attached to said supporting means, said secondlever rotatable in the same plane as said first lever means, projectionmeans on one of said levers, second projection means on one of saidlever means in spaced relationship along the length of said lever meansfroml said first projection, each one of said projection means on one'of said lever means alone contacting the other of said lever means for aportion of' all positions'of said first 1ever means, the total of saidportions equaling all positions of said first lever means, so that uponangular f movement of said first lever means, the resultant lever arm ofsaid first and said second lever means will change in length uponcontact to .the other lever means changing from said first to saidsecond projection means, ,as set by the attachment of said pivotalmounting means and moveable pick-up means mounted on said supportingmeans and connected to said second lever means to be displaced relativeto said supporting means in response to displacement of said moveablegauge point means. Y

8. In an extensometer, the combination including supporting means, fixedknife edge means attached to said supporting means, moveable knife edgemeans mounted on lever means pivotally attached to said supportingmeans, clamping means holding said knife edges in contact with aspecimen, adjustable resilient bracket means attaching said clampingmeans to said supporting means, a second lever means pivotally attachedto said supporting means between said speci-men and the pivotalattachment of said first lever means, projection means on one of saidlever means, second projection means on one of said lever means inspaced relationship along the length of said lever means from said firstprojection means, so that upon angular movement of said first levermeans, the resultant lever arm of said first and said second lever meanswill change in length upon contact to the other lever means changingfrom said first to second projection means, and moveable pick-up meansmounted on said supporting means and connected to said second levermeans to be displaced relative to said supporting means in -response ytodisplacement of said moveable knife edge.

9. In an extensometer, the combination including supporting means, fixedknife edge means attached .to said supporting means, moveable knife edgemeans mounted on lever means pivotally attached -to said supportingmeans, clamping means having portions for engaging a specimensubstantially opposite said knife edges, adjustable resilient bracketmeans attaching said clamping means to said supporting means, a secondlever means pivotally attached to said supporting means between saidspecimen and the pivotal attachment of said first lever means, aplurality of projection means of circular crosssection spaced along thelength of said first lever means, one of said projection meanscontacting said second lever means for a range of positions of saidfirst lever means so that upon angular movement of said first levermeans, the resultant lever arm of said first and said second lever meanswill change in length upon said second lever means changing contact fromone of said plurality of projection to another, and moveable pick-upmeans mounted on said supporting means and connected to said secondlever means to be displaced relative to said supporting means inresponse to displacement of said moveable gauge point means, anddifferential transformer means actuated by said pick-up means to emitvarying electrical currents corresponding to displacements of saidpick-up means.

10. In an extensometer, the combination including a @mgm llo'ac'iingsaidasecond leyer means-so as to urge said secv ondrlelver .meansAtoward said lever 'n'ieans, p`rojection imeans `on .one rof `said*vlex/e1' .meansv, `second .projection .means on oneeof Asaid lever meansrin spaced. relationship mongzthe length Lofsa'id levermeans Lfroxn.said ixst pro- 8 ""ieti'oumeans,l so mha't upon angular movemertf .fsidinst Hever means, *the resultant llover 'farm sof ."saidisrst and saidsecond lever means will nlangerin-'leng'thkupon ton'tact =t'o @the:other lever :means u changing'zfrzom said rst 'lrto second proj'edtionmeans, .and .moveableipickupzmeans "mount-:ed l'on said s'pporting meansan'd connected 1o said 'second-leverfmeans 1o be displacedirelative'stosaid-sup- Lpmin'g means in -nesponse fto displacement,-ofisaidxmoveablekie edge. v

flieiereees @ma -in theV niefof this 'patent IFGREI'GN PATENTS Y 553,505`Gemauy v. sept. '8, 1932

